The reason people use a small font is twofold: first, that they don’tknow their material well enough; second, they think that more text ismore convincing. Total bozosity. Force yourself to use no font smaller than thirty points. I guarantee it will make your presentations better because it requires you to find the most salient points and to know how to explain them well. If “thirty points,” is too dogmatic, the I offer you an algorithm: find out the age of the oldest person in your audience and divide it by two. That’s your optimal font size.